Sc'
Q. P. Code:755803 Class:F. Y. B'
QIA
Ans,
Subject : ChemistrY II
Date: 22-ll'2016
Correct option for MCQ( One mark each)
one medium to
The bending of a beam of light when it passes obliquely from
another is known as
(b) Refraction
Plant get water through the roots because of ------
i
ii
(a)
Capillary
of both reactant'
by the relation
the half time is related to the initiaiconcentration 'a'
io, u ,..ond order reaction with equal initial concentrations
lll
(b)
trEu
oc.
t'fa
to the reaction is
The number of molecules taking part in the step leading
of reaction.
lv
----
(c) molecularitY
Fullerene is an allotrope of
(b) carbon
SomeoftheGroup2meta|halidesinorganicsolvents.
halides, the one soluble in ethanol is
metal
following
the
Among
vl
(a) BeClz
vll
(a) Fluorine
vlll outer electronic configuration of Group
15 elements is
(c) ns2 np3
ix
xl
-'
of each others'
D and L-Lactic Acid are
(b) enantiomers
To find out absolute configuration of molecules'
Technique is used.
(c) x-ray diffraction
n-butane has maximum stability'
. .: ... . .. configuration of
(a) AntiPeriPlanar
xii
light
Racemic mixture rotates plane polarised
(b) in neither direction
B
ii)
iii)
C
True or False(One mark each)
of the reaction is always
For all chemical reactions the order and molecularity
same.( False)
period as we move from left to
Metallic character increases across the
right. ( False)
image then the molecule is
If a molecule is not superimposable on its mirror
chiral.( True)
Correct match)
Match the following ( One mark for each
Page 1 of 31
(1Mark)
Order of reaction (n) can be determined by using the equation
_/\-/\
toe\ttlr)
n=ffi+r
r-
los
\tt/r),
(1
log257
:.n=
-
log210
0.0877
+
0.og5a
+
Mark)
1
r
:0.939 + l:1.939 =2
Hence, the reaction is of
the second order.
(2 Marks)
OR
A
D
Derive an expression for the rate constant of a second order reaction with equal
initial concentrations of the two reactants.
An expression for the rate constant of a second order reaction with equal initial
concentrations of the two reactant
In the second order reactions, the rate of reaction is proportional to the
product of concentrations of two reactants. These two reacting molecules may
be same or different. Hence, the rate of reaction may be proportional to the
product ofa) two equal initial concentrations of the reactants (a: b), and
b) two unequal initial concentrations of the reactants (alb)
(l Mark)
The Expression for the rate constant with equal initial concentrationsconsider a reaction involving two molecules of the reactant A, i.e.
Products
2A
viz.
or the reaction of two different reactants having equal initial concentration
+
,
A+B->Products.
initial concentration of each of the reactant and 'x' mol
of the
dm-3 is the amount reacted in time 't'. Then, the concentration of each
reactant at time 't' can be given as (a-x) mol dm-3'
Let,a'mol
dm-3 be the
Therefore, the rate ofthe reaction can be given as-
Rate
dx
= fia
i.e.
(a
-
x)(a
#"@-x)2
Page 3 of 31
- x)
c) Two chiral carbons
i) Tartaric acid
ii) Liquid crystals d) Nematic Phase
e) Sodium
iii) Natrium
a) Antimony
iv) Stibium
b) dm3mol-lsec-t
v)Unit for second order reaction
e.2
Ans
A
i)
molecules (or atoms) whose concentration (or pressure)
determine the rate of the reaction is called the order of the reaction and the
number of molecules (or atoms) which take part in each step leading to
chemical reaction is called the molecularity of the reaction. In many cases, the
order and molecularity of a reaction is same, but there is no necessary
The number
of
correlation between the two.
pseudo first order reactions are generally bimolecular reactions which
follows first order kinetics. Even though the reaction involves two reactant
molecules, the rate of reaction depends on the concentration of only one
(2 Marks)
reactant and hence order of reaction ii one'
Any one suitable example with description
For e.g. - In Acid hydrolysis of methyl acetate
tf
catalvst
-
cHrcoocHr + H2O -+ cH3cooH +
CH3OH
above equation that two molecules, one each of methyl
But since water is
acetate and water are required for th e reaction to take place.
in excess, its concentration remains virtually constant. Consequently,
It is apparent from the
taken
depends only
even though the reaction is bimolecular, the kinetic of the reaction
should be of first
on the concentration of methyl acetate and hence the reaction
order.
(sucrose)
For e.g. - in case of acid catalysed inversion of cane sugar
FfcatalYst
+ CoHrzOo f C6H12O6
CnHzzOn + HzO
The rate of reaction depends only on amount of sucrose present'
ii)
(2
Marks)
when the
In a certain reaction, the half-.life time was found to be 257 minutes
initial pressure
initial pressure *u. i.613 x10s Nm-2 and it was 210 minutes at
was2* l0t Nm-t. Find the order of reaction'
Given:
(tr,r), = 257 mtns
(^,,), = 210mtns
;
;
ar
:
1.613
a2=2x
Page 2 of 31
x
lOs Nm-2
lOs Nm-2.
9o,=
K(o-x)'"" """O
(1Mark)
on rearranging the above equation, it becomes
Where K is a rate constant
On integrating the above equation, we get
o*
-.=xlat
l,
J @-x)z r
*
Il0-x) =Kt*C.........
where C is the integration constant.
At the start of reaction, when t 0 and
:
I:
0, the rate constant equation reduces
to
(a-o) =Kx0+C
a
'.!=
C
.........@
On substituting the above value in equation @,itbecomes
LL Kt*=
a
.i
la-x)
1
1
:. Kt =
- A
@_D;.Kt= a(a=* x),
:.K=
*6
.......@
@
order reaction having
The above expression is for the rate constant of second
equal initial concentrations of the reactants'
(3
ii)
Marks)
MolecularitY of the reaction
The rate law may or maY not
Order of the Reaction
1) The order of a reaction is the sum of l)
the number of molecules
the powers of concentrations in the rate indicate
which collide simultaneouslY for
law.
the reaction to take Place at the
levels of molecules
is
2) For the reaction, if the rate is 2) MolecularitY of the reaction
and it can
K[A]'[B]^, then order of reaction
is m+n
which can be zero also.
Page 4 of 31
always a whole number
not have zero value.
3) It can be defined as the number of 3) It
can be define as the number of
atoms or molecules whose concentration molecules
or atoms which take part
pressure determine the rate of in each
or
step leading
reaction.
to
chemical
reaction.
4) The order of a reaction changes with 4) The molecularity
depends on the
experimental conditions.
stoichiometry, hence, it is constant.
5) e.g.Hydrolysis of methyl acetate
CH3COOCH3
+ H2O
-CH,COOH
+ CH3OH
is a first order reaction.
5) e.g.Hydrolysis of methyl acetate
CH3COOCHg + HzO
-'+CHTCOOH + CHgOH
is a bimolecular reaction.
(Any 3 points 3Marks)
Page 5 of 31
B
i)
what is meant by the term viscosity of liquid? How is it
determined
(5)
expeflme
ntally?
i
.t:-.:-n"
I
I
I
jLf
! 'ir'],,:r,r:l br:f t'
i.i.rs.l
ii)
Explain the surface tension? Why rain drops are
surface tension.
Page 6 of 31
"....
,ph;iilii Write SI unit of
(3)
B
D
What are liquid crystals? Give its classifications
Page 7 of 31
(s)
ii)
The density of acetic acid at 293Kis 1.049
weight is 60. Calculate molecular refraction
is 1.3698"
Page 8 of 31
xl0ikg.m-j and i molecular
if the refractive i dex of acetic acid
(3)
C
In first order reactionif 25%o of the sample of cane sugar is hydrolyzed in 50
how long it will take for 50%oto be hydrolyzed?
Given-
t:
Change in concentration when
50 sec ,
the amount of cane sugar hydrolyzed - x:25Yo
.'.the change in concentration at
50 sec
:
(a
-x) :
100
-25
:
75oh
Let, initial concentration (a) :
For the first order reaction -
l00Yo i.e.when
Change in concentration at time
:. (aZ x) :
100
't'
is
x:
50%
- 50: 50 Yo
Page 9 of 31
t:0
s,
C
Q
OR
4t293 K, water formed 20 drops when flowing through the capillary of
iquid formed 39 drops.
x l0'kg.m-'and 0.82 x
face tension of liquid, if that of water is
3 A i)
Ans.
How does lithium differs from other alkali metals
(4)
?
Lithium differs from alkali metals in the following respects
:
(i) It is more harder and lighter than other alkali metals.
(ii) It is not affected by air easily and does not lose its luster even on
melting.
(iii) It reacts slowly with water to liberate hydrogen.
(iv) It does not react with oxygen below 00C. When burnt in air or
(v)
(vi)
(vii)
oxygen, it forms only monoxide, LizO. However, the rest of the
alkali metals give peroxides or superoxides. Lizo is much less basic
than oxides of other alkali metals.
Lithium is only alkali metal which directly reacts with nitrogen to
form Li3N
Lithium hydroxide decomposes at red heat
to form LizO.
Hydroxides of other alkali metals donot decompose.
zLiOH---r LizO + HzO
Lithium bicarbonate, LiHCO3 is known in solution but not in solid
state while the bicarbonates of other alkali metals are known in
Page 10 of 31
(viii)
solid state.
LizCOr is less stable, as it decomposes on heating.
LizCOg-LizO+COz
The other carbonates are stable.
(ix)
Lithium when heated with NH3 forms imide LI2NH while other
(x)
alkali metals form amides, MNHz
LiOH is much weaker base than NaOH or KOH.
Four differences
iD
-
4M (lM each)
In what ways does beryllium resembles with aluminium?
O
(iD
(iiD
(iv)
(v)
(vi)
In nature both the elements occur together in the mineral, beryl,
38eO.Al2Or.6SiOz
Both are not affected by atmosphere.
They do not decompose water.
Both become passive when treated with concentrated HNO3.
Both dissolve in caustic alkalies liberating hydrogen.
Be + 2NaOH -r NazBeOz +IIz
Al + 2NaOH+ ZH2O + 2NaAlzOz+ 3EIz
Both BeO and AlzOl are amphoteric in nature. Oxides are extremely
hard and have high melting points.
BeO+HzSO++BeSOa+HzO
BeO + 2NaOH
- NazBeO z *HzO
(viD
(viii)
(ix)
Al2O3 + 6HCl +2AlClz+ 3HzO
Al2O3 + 2NaOH
2NaAlOz + HzO.
+
Beryllium carbide(Be2c) and aluminium carbide (Alac3) both
evolve methane on treatment with water
Be2C+2IlzO+2BeO+CFI4
AlaCr + 6I{20
-2AlzOs+ 3CFI4
Beryllium and aluminium both form polymeric covalent hydrides.
Both combine with nitrogen when strongly heated in its
atmosphere.
3Be +Nz
-
BelNz
2Al+N2+2AlN
(x)
(xi)
(xii)
Nitrides on action with water evolve ammonia.
Be3N + 6HzO * 3Be(OH)2 + 2NH3
AIN + 3H2O -'AI(OH): + NHr
Both metals are obtained by the electrolysis of their fused salts in
the presence of fluorides.
The carbonates of both the metals are unstable
The salts of both Be and Al do not impart a colour to the flame
Page 11 of 31
when heated in it.
Four ways of resemblance
-
4M (lM each)
OR
A i)
Explain the anomalous behaviour of nitrogen.
The important points in which nitrogen differs from other members
are listed below
of l5 group
:
l.
Nitrogen is a gas while other members are solids.
2. Nitrogen molecule is diatomic (N=N) while other elements form tetra
atomic molecules such as pa, Asa and Sb+.
3- The catenation property is more pronounced in nitrogen. Chains
containing upto eight nitrogens are known but in the case of other
elements, catenation is limited to two atoms only.
4. Nitrogen forms five oxides. N2O(nitrous oxide), NO(nitric oxide),
N2o3(nitrogen trioxide), No2(nihogen dioxide) and N2o5(nitrogen
pentoxide). others can form at the most three types of oxides,
&o:,
XzO+,XzOs.
NzOs and N2O5 are monomeric
in nature but oxides of other elements
are dimeric.
5.
6.
Hydride
of
nitrogen OIH3) is stable while the hydrides of other
elements are not stable. Hydrogen bonding is present in ammonia
(NHt but not present in other hydrides.
Except NF3, the haloides of nitrogen (NCl:, NBr3 and NI3) are unstable
and explosive. The halides of other elements are stable. Unlike p. As
and Sb, nitrogen does not form pentahalides.
7. Due to small size and high electronrgativity, nitrogen can form
trinegative ion N-3. This terrdency is less
in P but absent in
other
elements.
8.
9.
As nitrogen does not have d orbitals in its valency shell, its maximum
covalency is 3 while to the case of other elements, the maximum
covaleny is 5
Nitrogen does not form sulphide while other elements form sulphides.
Four points of anomalous behaviour
iD
-
4M (lM each)
What is diagonal relationship ? Explain it with respect to boron and silicon.
Boron shows resemblance with silicon, the second typical element of group
l4 of the next higher period. This type of relationship between diagonally
Page 12 of 31
placed elements is called diagonal relationship
Diagonal relationship concept
Group
13
Secondperiod
B
period
Al
Third
- lM,
Group 14
C
Si
Following are the properties where boron and silicon show close
resemblance:
O
(ii)
(iiD
(iv)
(v)
(vi)
Both boron and silicon are non-metals. Both have high melting
points [B :2300 oC ; Si: 14l00C], high ionisation energies (B =
8.3ev, si : 8.20 ev) and are bad conductors of electricity at normal
temperature.
Both have nearly equal electronegativity B:2.0; Si : l.g
Both boron and silicon show allotropy.
Most of the compounds of boron and silicon are covalent.
:tr"#lH'#,l*il;ilil1.:"#:"f,,T,T"T:
:*ffJffi"'o,
alkalies forming borate and silicates respectively.
BzOr + 6NaOH + 2NalBO3 + 3I{2O
SiO2 + 2NaOH + NazSiOr + FIzO
Both boron and silicon combine with metals to form borides and
silicides respectively.
28 + 3Mg -'MgrBz
Si+2Mg+Mg2Si
3 points for explanation of diagram. relationship
3Marks (1 Mark each)
B i)
between
B and Si -
Quote any four uses of calcium carbonate.
Industrial applications
1. The main
use of calcium carbonate is in the construction industry,
either as a building material or limestone aggregate for road building or
as an ingredient of cement or as the starting material for the preparation
Page 13 of 31
of builder's
mainly caus
Ionger used for building
substance for building m
2.
also used in
The carbonate
lag with variou
3.
calcium
and filte
reases th
added to drilling fluids as a
agent; it is aGoi weigtrting
drilling fluids to contril the
Calcium carbonate is added to swimming pools, as
a pH corrector for maintaining alkalinity
and offsetting th;
properties of the disinfectant agent.
".iai.
Health and dietary applications
4'
5.
Calcium carbonate is widely used medicinally as an inexpensive
dietary
calcium supplement
I antacid.
or
It may be
used
as a phosphate binder for the
of hyperphosphatemia (primarily in
6. It is also used in the
put
pharmaceutical industry
inert filler for tablets and other pharmaceuticals.
7
'
.
as
an
Calcium carbonate is used in the production of calcium oxide as
well as
toothpaste.
Agricultural
8.
treatment
use
Aericultural lime, powdered chalk or limestone, is used as a cheap
method for neutralising acidic soil, making it suitable for planting.
Environmental applications
9.
Currently calcium carbonate is used to neutralize acidic conditions in
both soil and water.
10. Calcium carbonate
is also used in flue gas desulfurisation applications
eliminating harmful SOz and NOz emissions from coal and other fossil
fuels burnt in large fossil fuel power stations.
Four uses - 4M (lM each)
ii)
How is sodium carbonate prepared ? state any two of its properties.
Preparation
This process was developed by Chinese chemist HouDebang in the 1930s. The
earlier steam reforming byproduct carbon dioxide was pumped through a
saturated solution of sodium chloride and ammonia to produce sodium
Page 14 of 31
bicarbonate by these reactions:
NH3
*
COz + I{zO
-'
NII4HCO3
NFI+HCOI + NaCl
NII+CI + NaHCOT
The sodium bicarbonate was collected as a precipitate due to its low solubilitv
and then heated to yield pure sodium carbonate
-
2 NaHCOa
+
NazCOl + HzO + COz
one method preparation
- wording (1M),chemical
equations(lM)
Properties
l.
Sodium carbonate is a white crystalline powder with a density of 2.54
glmL,and a melting point of
g5
I
oC.
2. It is a stable but hygroscopic solid (absorbs
water from air) and readily
dissolves in water to form weakly acidic carbonic acid and the strong
base, sodium hydroxide.
3. The aqueous solution ofNa2CO3 is overall a strong base. It reacts
violently with many acids.
4.
When heated to high temperatures, it decomposes to emit toxic fumes
of disodium oxide (NazO).
Two properties
- 2M(lM
each)
OR
B D
Mention any four uses of sodium bicarbonate.
Pest control
1.Used to
kill
cockroaches. Once consumed,-it causes internal organs
cockroaches to burst due to gas collection.@
of
Paint and corrosion removal
2.Sodium bicarbonate is used in a process for removing paint and corrosion
called sodablasting; the process is particularly suitable for cleaning aluminium
panels which can be distorted by other types of abrasive.
Alkalinity/pH increase
3.It can be administered to pools, spas, and garden ponds to raise the total
alkalinity, this will also raise the pfl level and make maintaining proper pH
easier.
Page 15 of 31
Pyrotechnics
4.Sodium bicarbonate is one of the main components ofthe
common incendiary "black snake" firework. The effect is caused by the
thermal decomposition, which produces carbon dioxide gas to producr u
long snake-like ash as a combustion product of the other main
component, sucrose.
Mild disinfectant
5.It has weak disinfectant properties, and it may be an
effective fungicide against some organisms. Because baking soda will absorb
musty smells, it has become a reliable method for used-book sellers when
making books less malodorous.
F'ire extinguisher
6.Sodium bicarbonate can be used to extinguish small grease or electrical fires
by being thrown over the fire, as heating of sodium bicarbonate releases carbon
dioxide.
Medical uses
T.Sodium bicarbonate mixed with water can be used as an antacid to treat acid
indi gestion and heartburn.
Personal hygiene
8.Sodium bicarbonate is also used as an ingredient in some mouthwashes. It
has anticaries and abrasive properties. It works as a mechanical cleanser on the
teeth and guflS, neutralises the production of acid in the mouth, and also acts as
an antiseptic to help prevent infections.
In sports
9.Small amounts of sodium bicarbonate have been shown to be useful as a
supplement for athletes in speed-based events, such as middle-distance
running, lasting from about one to seven minutes.
As a cleaning agent
lO.Baking soda is commonly added to washing machines as a replacement for
softener and to remove odors from clothes. Sodium bicarbonate is also
effective in removing heavy tea and coffee stains from cups when diluted with
warm water
Four uses - 4M (lM each)
iD
Write any one method of preparation and two properties of sodium hydroxide.
Preparation
By chlor alkali process (Solvey process) - It is electrolysis of brine
Page 15
of31
The overall reaction for the electrolysis of brine is
2NaCl + 2H2O
:
+ Clz+ H2 + 2NaOH
one method preparation
- wording (rM), chemicar equation (1M)
Physical properties
1.
Pure sodium hydroxide is a whitish solid, sold in pellets,
flakes, and
granular form, as well as in solution. It is highly *lubl"
in water, with a
lower solubility in ethanol and methanol, bui is insoluble in
ether and
other non-polar solvents.
2.
Similar to the hydration of sulfuric acid, dissolution of solid
sodium
hydroxide in water is a highly
i-n which a large
amount of heat is liberated, posing a threat to safety through
the
possibility of splashing. The resulting solution is usually c-olourless
and
odorless. As with other alkaline solutions, it feels slippery when
it
comes in contact with skin.
.toth.*i.-r.*ti*
Chemical properties
3.
Reaction with acids
Sodium hydroxide reacts with protic acids to produce water and the
corresponding salts. For example, when sodium hydroxide reacts
with hydrochloric acid, sodium chloride is formed:
NaOH(a) + HCI(aq)
NaCl(aq) + H"O[)
-
In general, such neutralization reactions are represented by one simple net
ionic equation:
OFf(aq)+rf(aq)*HzO(D
4.
Precipitant
Aluminium hydroxide is used as a gelatinous flocculant to filter out particulate
matter in water treatment. Aluminium hydroxide is prepared at the treatment
plant from aluminium sulfate by reacting it with sodium hydroxide.
AI2(SO4)3 + 6 NaOH
2 AI(OH): + 3 NazSO+
-
Two properties
c
- 2M (lM
each)
Defrne nitrides. Compare the properties of nitrides of alkali and alkaline earth
metals.
Nitrides forms binary compounds with elements having similar or lesser
electronegativity. These compounds are called nitrides and they contain nitride
Page 17 of 31
ion N-3.
Definition _ lM
l.Only Lithium reacts with nitrogen, which it reduces to
the nitride ion
6Li + N2 A- 2Li:N
2. All the alkaline earth metals burn in air to form nitrides of
the type M3N2.
3M+Nr-M3N2
The ease of formation of nitrides decreases from Be
to Ba.
3.This is in contrast to alkali metals where only Li3N is formed.
Because the Nz
molecule is very stable, it requires very high energy to form
N3- ions. The large
amount of energy is evolved when the crystalline solid is
formed. The lattice
energy is particularly high because of the high charges ofthe
ions I\rf2 and N-3 .
4.BetNz is volatile (covalent character) while other nitrides
are not as they are
ionic crystalline solids.
Three comparative properties _ 3M
(lM
each)
OR
C
what are oxides ? Explain the different types of oxides formed by alkali and
alkaline earth metals.
oxides are binary compounds of oxygen with an element less electronegative
than oxygen itself.
The alkali metals form mainly three types of oxides normal oxides
), peroxides IMzOz (Or2') and superoxides MOz (Oz).
(D
I\&o
(o2-
Normal oxides It&o - They are obtained by burning the metal in a
limited supply of air or oxygen. These oxides are highly soluble and
strongly basic.
4M+02-2MzO
(ii)
Lizo is most stable oxide of this type than other alkali metals.
Peroxide lvboz- All alkali metals form peroxides. The peroxides
are prepared by heating the normal oxide at773Kin air.
2LizO +773KLizOz+ ZLi
Page 18 of 31
(iiD
Superoxides (Moz)
-
The superoxides are obtained by heating the
peroxide with oxygen under pressure except
lithium and sodium,
the remaining alkali metals form superoxides (Ko2,
Rbo2, cso2)
The above type of oxides readily react with
water. They can be distinguished
from each other by the products formed during their
hydrolysis reaction.
(Normal oxide) i\&O + I{zO
(peroxides)
-
2MOH (no HzOzand Oz)
wo2+ 2uro + MoH +Hzoz+ ll2oz(both H2o2 and 02)
The alkaline earth elements form two types of oxides
(i)
Normal oxides (O22) MO
(ii)
Peroxides (O22-) MO2
:
Except Ba and Ra, these elements when burnt in oxygen
form oxides of the
type MO
2M+ gr-+ 2MO
Beryllium metal is relatively unreactive and does not react below
6000c, but
the powder form is much more reactive and burns brilliantly.
The element, Mg
burns with dazzling brilliance evolving a lot of heat.
Barium and radium, being highly electropositive, form peroxides. However,
the tendency to form peroxides from oxides is in the order
CaO<SrOcBaO<RaO as the size of metal ion increases.
Ba + Q,
-'
BaO
*
02 --+ BaQ2
Thus the affinity for oxygen increases on moving down the group.
Be < Mg <Ca<Sr< Ba
Oxides concept
Page 19 of 31
- lM,
Oxide(example and explanation)-
lM,
Peroxide (example and explanation)-
lM,
Superoxide (example and explanation) _
Explain the following terms with suitable example:
a) Enantiomers.
The optical isomers which are non-super imposable
mirror images are
called as enantiomers.(l mark)
Example-
cooH
u-fon
CHe
cooH
no$n
CHs
Enantiomers of lactic acid
(l
mark)
b) Meso form
The optically inactive compound, with chiral centers having plane
of
,
symmetry is known as meso compound.
(1 mark)
cooH
-
___.!|L_o_r:t___
-
tf+-,t;----
Plane of sYmmetry
cooH
Meso tartaric
acid
(l
mark) Any other example may be
considered for both.
ii)
Assign R or S descriptors to the following compounds:-
cHo
1)
Priority order
2)
Priority order
Page 20 of 31
lM
Br > -CHO > -CI{2OH >
Configuration-
_H
OH
R
> -CN > _CHs > -tt
Configuration_ R
Priority order
(1
mark)
(1
mark)
Configuration
OR
A i)
What is conformation? Explain the
conformations of ethane and comment
on their relative stabilities
conformation:- Different arrangements
of atoms or groups in three
dimensional space arising due to rotation
around r*bon- carbon single
bond.(t mark)
Molecule of ethane shows two major
conformations:_
Eclipsed: In which all hydrogen atoms
on adjacent carbon are close to each
other.
H
(1 mark)
Staggered:- In which all hydrogen atoms on
adjacent carbon are as away as
possible from each other.
(1 mark)
staggered conformation is more stable than eclipsed(r mark)
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ii)
Define diastereoisomers. Enlist diastereoisomers
from following:-
H
f
H
H
H
HO
II
Br
H
ru
Diastereoisomers:- optical isomers which are non-super
imposable isomers
but are not mirror images of eaoh other. (1 mark)
Diastereoisomeric pairs in given example:-
i)I
and
III ii) I and IV iii) II and III iv) II and IV
(1.5 mark each for any two correct pairs)
B i)
Label the following structures with Erythro and Threo notations.
eH^
CHO
H
H
l)
OH
2l
HO
H
H
CHs
l)Erythro
2) Threo
ii) Assign
(2 marks each)
E or Z descriptors to the following:-
CoHs
l)
2)
Hsc
Priority order: 1) C6H5> CII3 and Br > Cl(l mark)
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Configuration ,,E"
(1 mark)
2)I >H and Br>CI(lmark)
Configuration "E"
(1 mark)
OR
B I)
convert foilowing Fischer projection formula
to Newman projection
formula:-
l)
Hcl
2)
Hcr
cH2oH
ii)
Assign "D" or
"L" or "cis" or
following:-
"Trans,, whichever applicable to the
3)
t\-,/tt'o,
,."A,
Answers:- 1) erprr 2) et1, 3)
C
Trans
A'|
cl
-) "KZ
4) Cis.( 1 mark each)
which of the following compounds have chiral carbon:-
l)
2)
CH3CHBT2
CH3CHCIC2H5
cHo
3) er-j-H
I
4)
cH3cH2cHBrcH2cH3
I
cH2oH
Answers:-Compounds with chiral carbon :- 2 and 3.
( Two marks for each correct answer)
OR
C
what is Racemic mixture? what is resolution of racemic mixture?
Racemic mixture:-It is a mixture containing equal amounts of
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..d' and,,l,
forms of optically active compound.
Mixture is optically inactive because of
external compensation of rotation.
( 2-Marks)
Resolution of racemic mixture:-process
of separating racemic mixture
into component enantiomers is known
as resolution.
(
2-Marks)
Q.s
Attempt any four of the following
S
Explain ostwald's isolation method used in the determination
of order of a
reaction.
ostwald's isolation method is based on the principle that, if
a1 the reactants
except one are taken in a large excess so that their
concentrations (or
pressures) will remain practically constant. The
order of the reaction will
then be determined by the number of molecules thus isolated.
(2-Marks)
Let a reaction involves n1 molecules of the reactant A, n2 molecules
of the
reactant B and n3 molecules of the reactant c, then the rate
of reaction can be
given as-
Rate q.
ci,c['c["
and the total order of reaction .n, can be given as
If, the reactants 'B' and
n:
flr
* nz * nl
'c' are taken in an excess, then the rate depends
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only
on the concentration of reactant 'A' and is
independent of that of reactants
'B' and 'C'. thus, the order of the reaction will be ,n1,.
Similarly, 'n2' and'n3' can also be evaluated
by taking reactants A &
A & B respectively in large excess.
and
e.g. consider the reaction between silver
acetate and sodium
2CH3COOAg
+
HCOONa-+ 2Ag
+
CH3COONa
+
c
format+
CH3COOH
+
COz
In this reaction when the silver acetate is taken in
large excess, the
reaction is found to be of first order with respect
to sodium formate. on the
other hand, when sodium formate is taken in
large excess, it is found to be of
second order with respect to silver acetate.
(3-Marks)
Describe the Stalagmometer method used to determine
Surface tension of
liquid
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the
(5)
Write a note on (i) acid rain (ii) photo chemical smog.
i)Acid Rain
- The term 'acid rain' is used to describe all precipitations Page 25 of 31
rain, snow, fog, dew _ which are more
acidic than normal.
(lMark)
source -The normal rain is slightly acidic
having pH of about 5.6 as carbon
dioxide gas reacts with it to form a weak
carbonic acid.
(%Mark)
CO2 + H2O
+
H2CO3 (carbonic acid _ weak acid)
Acid rain results mainry from the presence
of two strong acids in polluted air
: FIzSOa and to a lesser extent, HNO3.
The presence of hydrogen sulphide and chlorine
in the atmosphere also
contributes to the formation of acid rain.
Consequences
-
Drop in pH of lakes and rivers can destroy ecological
balance. Most aquatic
animals cannot survie when pH is less than 4.
Due to acidic rain leaf pigments are decolourised
and agricultural
productivity if deceased.
Metallic surfaces exposed to acid rain are readily corroded.
Textile fabrics,
paper and leather products lose their material strength
or disintegrate by the
acid rain.
Acidic drinking water can cause damage to kidney and liver and
diarrhoea in
young children.
Ways to minimize
An international programme, involving all the countries in order to take
concrete measures to minimisesulphur dioxide pollution which
travels very
fast in atmosphere, is the need ofthe hour.
Use of LPG in place of coal, kerosene or firewood.
(One effect or way to minimize _
lMark)
Photochemical smog
smog means smoke and fog. photochemical smog is also called Los Angeles
smog as it was observed for the first time in Los Angeles in 1950. This type
of smog is formed by combination of particulates (smoke, dust, fog) with
Page 27 of 3L
oxides of nitrogen and hydrocarbons
in presence of sunlight. As
photochemical reactions are invorved
in the
formation ofimog, it is cared
photochemical smog
(1-Mark)
It occurs in those areas which have warm,
sunny and dry climate align with
the atmosphere has large concentration
of automobile exhausts.
Formation - Nitric oxide released into
the atmosphere is quickly oxidized
to
nitrogen
dioxide.
2NO + Oz -+ 2NOz
Sunlight causes photochemical decomposition
of Noz (waverength shorter
than 400nm) into NO and O.
NO2+hv-+NO+O
Atomic oxygen combines with traces of hydrocarbons
present in atmosphere
and produces materiars which are responsible
for photochemical smog.
(%Mark)
Effects
-
It causes eye initation, cough, chest discomfort and
fatigue to humans.
compared to human beings, vegetation is more prone
to the harmful effects
of oxidants. Organic oxidants act as poisons to plants.
Control
Installation of efficient catalytic converters in the automobiles
The compound like dimethylhydroxylamine can be
sprayed to the atmosphere
which possess smog inhibiting characteristics.(haps free radical
precursors of
photochemical smog.
(One effect or way to minimize _
What is inert pair effect ? Explain with suitable examples.
Inert pair effect
1.
The inert pair effect is the tendency of the electrons in the
outermost atomic g orbital to remain unionized or unshared in
Page 28 of 31
lMark)
)
a
J.
4.
The same trend in stability is noted in groups
14, rsand 16. As such
the heaviest members of the groups, e.g.
lead,
bismuth
and poloniunx are comparatively stable
in oxidation states
*4 respectively.
*2, +3, and
5. The lower oxiidation
state in each of the elements in question has
2
valence electrons in s - orbitals. valence electrons
in an s orbital are
more tightly bound and are of lower energy than
electrons in p
orbitals and therefore less likely to be involved in
bonding.
Concept
- l-Mark
Two examples
- 2-Marks
Explanation
- l-Mark
Consequence
- l-Mark
Draw various confonnations of n-butane obtained by rotation
around Cz_ct
bond and write a note on their relative stabilities.
l) Antiperiplanar
2)
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Anticlinal
3) Synclinal (Gauche)
4) Synperiplanar
Relative stabilities:.-Antiperiplanar, minimum
energy most stable.
Anticlinal, less stable than Antiperiplanar and Synclinal
(Gauche) but more
stable than Synperiplanar.
Synclinal (Gauche) less stable than Antiperiplanar
but more stable than
anticlinal and synperiplanr
Synperiplanar, maximum energy least stable.
(Half mark for each correct conformation.)
(Two marks for relative stability explanation.)
F
What are geometric isomers? Explain geometrical isomerism
in olefins and
cyclic compounds with suitable examples.
Geometric isomers:-Compounds having the same structure
but different
spatial affangement of groups around C:C or restricted rotation
in substituted
cyclic compounds are called as geometric
(lMark)
isomers.
Geometrical isomerism in olefins
As double bond is formed by lateral overlapping of p-orbitals, rotation
around
is restricted. Hence substituted olefins exhibit the phenomenon of
geometric
(lMark)
it
isomerism.
Example: 2-butene is having two geometric isomers.
HsCr_rCHg HgC\ )1
,:\
HHFibn,
cis-2_butene
trans;_2_butene
llMarg
Geometrical isomerism in cyclic compounds
In cyclic compounds ring takes the place of rigid double bond and restrict the
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rotation of carbon atoms about their axis. This results phenomenon
in
geometric isomerism in substituted cyclic compounds.
Example: l,3-dimethylcyolobutane is having two geometric isomers.
cis-isomer
trans-isomer
(lMark)
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